Reversing mechanism



May 3, 1938.

R. R CHAPPELL. El AL REVERSING MECHANISM Filed April 25, 1936 2Sheets-Sheet l /fil g yer 5. C o 7 ATTORNEY.

y K- R. R. CHAPPELL ET AL 2,116,142

' RE VERSING MECHANISM Filed April 735, 1936 2 Sheets-Sheet 2 g; 4 3Lwig.

ATTORNEY,

Patented May 3, 1938 UNITED STATES PATENT OFFICE REVERSING MEGHANISMporation of Delaware Application April 25, 1936, Serial No. 76,448

13 Claims.

This invention relates to a mechanical movement and more. particularlyto means designed to secure reciprocating movement of one part relativeto another.

It has been heretofore proposed to produce reciprocatory movement bycausing a movable part to follow the path of a groove in a cooperatingpart such, for example, as .the axial reciprocation which may be securedthrough the reaction of a continuous or endless helical groove in thesurface of a rotatable cylindrical member, as shown in Au Patent No.1,645,273. In such prior apparatus, however, there has resulted adisturbance in the desired ratio of movement between the reciprocatingand rotary parts at the point where the reversal of movement of theformer occurs.

It is accordingly an object of the present invention to provide novelapparatus of the above character wherein a sharp, substantiallyinstantaneous reversal in the movement of the reciprocating part isobtained.

.Another object isto provide novel means for converting rotary movementinto reciprocatory movement in a direction parallel to the axis of therotating element whereby the ratio between said movements may bemaintained constant throughout the entire range. of movement of thereciprocating part.

The above and further objects and novel features of the invention willmore fully appear from the following detail description when taken inconnection with the accompanying drawings. It is to be expresslyunderstood, however, that the drawings are for the purpose ofillustration only and are not designed as a definition of the limits ofthe invention, reference being primarily had for this latter purpose tothe appended claims.

In the drawings, wherein like reference characters refer to like partsthroughout the several views,

Fig. l is a side elevation of one'form of mechanism embodying thepresent invention;

Fig. 2 is a top plan on an enlarged scale and with parts broken away ofthe device of Fig. 1;

Fig. 3 is an enlarged top plan, partly in section and with parts brokenaway, showing the reciprocating member at the point of reversal, thesection being taken substantially on line 33 of Fig. 4;

Fig. 4 is a section taken substantially on line 4-4 of Fig. 3, the guidemeans of the reciprocating part being seen in side elevation;

Fig. 5 is a bottom view of said guide means;

Fig. 6 is an enlarged detail View taken substantially onthe arcuate line6- 6 of Fig. 4;

Fig. 7 is a similar viewshowing a modified form of the guide. means;and,

Fig. 8 is a diagrammatic view illustrating the error which occurs in theoperation of similar apparatus heretofore provided. 5

One embodiment of the present invention is illustrated in the drawingsby way of example in the form of a device wherein a cylindrical memberhas an endless thread on the surface thereof, said thread beingpreferably formed by cutting right-hand and left-hand helical grooves insaid surface, each of said grooves terminating'at an intersection withthe other and having an axial length substantially equal to the desiredextent of the reciprocating movement. The endless groove thus formed iscaused to coact with a member which is constrained to move in a straightline so that when the cylinder is rotated a reciprocating movement in aline parallel to the axis of the cylinder is imparted to said mem- Ober. The pitch of both of the grooves is preferably the same and isdetermined by the desired ratio of movement between the rotary memberand the reciprocating member associated therewith. If the axial lengthof the grooves is greater than one-half the pitch thereof, the same willintersect and cross each other. Means are provided on the reciprocatingmember to prevent shifting of the same from one groove into another at apoint of crossing, and means are also provided for obtaining a reversalof the movement of said member at the end of the groove withoutdisturbing the ratio of movement between the same and the cylinder.

For the purpose of illustration, the endless screw is shown as beingrotatably driven by a weight and float in accordance with changes in aliquid level, but any suitable driving means, such as a motor, manualpower, a. clock, etc., may be employed. It will also be apparent that insome embodiments of the. invention, the recipro-' cable element may bethe driving member and the cylinder the driven member, and in others thereciprocating movement of a member, as the phrase is herein used, mayconstitute only one component of the true movement of that member. Itwill also be seen that the grooved surface may take other forms than acylinder. The means to be reciprocated, as shown, comprises a carriagebearing a suitable recording style which is adapted to cooperate with arecording surface to print a graph indicative of the positions of saidfloat and hence the liquid level, but it may take the form of any one ofa great variety of elements to which it is desirable to impartreciprocating movement.

Referring now to the drawings and more particularly to Figs. 1 and 2, adrum or cylinder Ill is rotatably mounted in bearings on a pair ofspaced supports H with the shaft l2 thereof extending through one of thesupports and having a suitable pulley or wheel I3 keyed thereon. A cordor cable l B is wound around said wheel and has a float I5 secured toone end thereof, said float resting upon the surface of a body of water,the stage of which is to be recorded. A weight it is secured to theother end of cable 54 for keeping the latter taut between the float andwheel l3 and for rotating the latter when the liquid level rises. Thefloat and weight thus constitute one of the many suitable forms ofdriving means which may be employed for rotating cylinder I0, otherforms of which will be apparent to those skilled in the art.

The surface of cylinder in has inscribed therein an endless threadcomprising two grooves I6 and il, one of which follows the course of alefthand and the other of a right-hand screw thread, the pitches of thesame being shown equal and uniform. The two grooves cross each other atpoints l8 (Fig. 2) and terminate at points of intersection 59 adjacentthe ends of cylinder H]. The walls 20 and. 25 of groove I6 continue atsaid latter points without change of pitch until intersected by walls 22and 23, respectively, of groove ll, which also extend to the lines ofintersection without change of pitch. The surface of cylinder [0 ismilled out or cut away over a somewhat rectangular area 24 adjacent theends of grooves l5, H but to a less depth than said grooves, as will beclearly seen in Fig. 4.

The carriage constituting the reciprocating element of the illustratedembodiment, which element, as heretofore pointed out, may assume variousother forms, comprises a frame 25 that is constrained to move in arectilinear path by a pair of vertically spaced tracks 26 and 2'!supported by standards I I and on which tracks said frame is movablymounted by means of four grooved wheels 28.

A recording style 29 is adjustably mounted on carriage 25 and adapted toengage a recording sheet 38 on drum 3!. The latter may be rotated andthe movement thereof controlled in any suitable manner by any of severalcommon and wellknown means for the purpose, such as by a weight 32secured to cord 33 wound around one end of drum 3i. The turning movementof the latter may be controlled by timing mechanism 34. The driving andcontrol means for drum 3| as well as the drum itself, carriage 25 andstyle 29 may be of usual or any suitable or desired construc-- tion, andsince the same do not per se form any part of the present invention, itis believed to be unnecessary to show and describe the same in furtherdetail.

Heretofore in apparatus of the general character of the presentinvention, the carriage or other reciprocable part has been providedwith a roller which coacts with the walls of the grooves or threads onthe rotating member for securing the desired movement. In suchapparatus, however, the ratio of movement between the reciprocating androtating parts is disturbed when said reciprocating part is near thelimits of its movement, i. e. near the ends I!) of grooves l6 and H. Theerror which occurs in the operation of such apparatus is illustrated inFig. 8 wherein it appears that the center of a roller 35 or other guidemember travels along a path ABC rather than along the ideal path AOC.

For the purpose of analysis, let us consider roller 35 as moving ingroove [6 with the same forces acting thereon that would be acting ifthe grooved member It! were moving in the direction of the single-headedarrow. Under these conditions, the pressure and reaction thereto wouldoccur between wall 20 of the groove and the surface of the roller, andthe center of the latter would follow the path XA. When the position Ais reached, the only pressure exerted and. reaction thereto would stilloccur between the roller and wall 20' so that the center of the rollerwould follow an arcuate path AB having a radius equal to that of theroller. When the roller has reached point B, it will be seen that noforce will be exerted thereon by the member I0 until wall 23 of groovel1 moves into contact therewith or, in other words, the roller would, inactual operation, remain stationary while the driving element l0 moves adistance represented by the straight line CB.

Accordingly, when roller 35 is constrained to move in a straight lineXZ, it will be apparent that during the reciprocating movement thereoffrom A to Y, the ratio of such movement to the movement of member ID inthe direction of the arrow varies greatly, i. e. from the normal desiredvalue to zero. Additionally, the direction of movement of thereciprocating part 35 is reversed at Y after an interval of rest insteadof traveling to point Z. This error may of course be reduced bydecreasing the size of the roller, but the same cannot be eliminatedwhen pressure on the roller is depended upon at the point of reversal.

Novel means are accordingly provided whereby a desired ratio of movementbetween the reciprocating and rotating members is never disturbed andthe reversal of movement of the element to be reciprocated issubstantially instantaneous. Such means as shown are constituted by apart of carriage 25 and comprise a bolt or spindle 36 which is supportedon frame 25 by means of a flanged collar 31 and extends downwardlytherefrom, as viewed in Fig. 4, to a point adjacent the bottom of threador grooves IS, IT.

Loosely mounted on pin 36 adjacent collar 31 is an elongated boat orguide member having an upper flange 3B and a depending portion 39, thewidth of the latter being slightly less than that of grooves 16, ll.Said depending portion 39 projects into the groove to an extent suchthat the curved lower face thereof will clear the surface of milledspaces 24 at each end of cylinder l0 and permit the ends of the boat toswing about pin 36 in said spaces during the reversal of movement of thepin. Said guide or boat is sufliciently long to bridge the crossinggroove at points 18 when pin 36 is moving past one of said points tothereby prevent said pin from shifting from one groove into another. Theabove is the sole purpose of guides 38, 38, the same having no effectwhatever on the reversal of movement of pin 36 at the points l9.

Also mounted on pin 36, either loosely or rigidly, is a reversing guide40 which, in the form shown in Fig. 6, is diamond shaped, with twoopposed sides parallel to walls 20, 2| of groove l6 and the other twosides parallel to walls 22, 23 of groove IT. The perpendicular distancebetween each pair of said parallel sides is preferably slightly lessthan the width of grooves l6, ll. As best seen in Fig. 4, member 40 ispreferably mounted on pin 36 so as to occupy a position in grooves I6,I! below the surface of area. 24.

In order to minimize the force required to be exerted by cylinder ID orothermovable member to impart rectilinear movement to carriage 25, aroller 41, having a diameter substantially the same as the width ofgrooves l6, I1, is rotatably mounted on the lower end of pin 36. Aworking clearance is of course allowed for said roller, and suchclearance is preferably less than the working clearance allowed formember 46 so that the only friction between the rotatable andreciprocating parts except as will appear hereafter will be a rollingfriction.

In operation, as cylinder i6 is rotated, carriage 25 is moved in astraight line parallel to the axis of the cylinder, 1. e. along tracks26, 27, by the coaction of groove l6, for example, and roller 4|. Whenroller 4| reaches a point of intersection l6, guide 38 is operative toeffectively bridge groove ll so that said roller will continue in,groove l6 until it reaches point [9 at one end of said groove. Member 46will also perform this same function. When the center of roller 4|reaches a point in groove [6 corresponding to point A of Fig. 8, thepressure being exerted by wall 26 of groove IE will be shifted from theroller to the trailing portion of the side wall of guide 46, therebycausing pin 36 to continue its rectilinear movement without any changein the ratio of said movement to the movement of cylinder l6. Atsubstantially the same instant that wall 26 ceases to engage the side ofmember 46, roller 4! will be engaged by wall 23 of groove [1, therebyinstantly reversing the direction of movement of carriage 25 without anydisturbance in the ratio of movements. When, and only when, the point ofreversal, i9 is reached, guide boat 38, 36 will be caused to swing bycontact with the intersections of wallsZfl and 22 into the dotted linepositions of Fig. 3 as roller 4| and member 46 start to move along thecenter line of groove IT. It will be noted that if member 46 were notprovided, boat 38, 39 would start swinging when the roller reaches pointA (Fig. 8) and gradually assume its new position in line with groove ll,said new position being reached only after the roller has moved pastpoint C.

In the modification shown in Fig. '7, the leading and trailing points ofthe diamond shaped reversing guide are removed, thus leaving a hexagonalguide member 42. The latter may also assume other shapes, it beingnecessary only that the relatively short operative portions of theparallel sides thereof be retained.

There is thus provided novel means for securing reciprocating movementof a propelled part by causing the same to coact with a cam surface on adriving part, whereby a constant ratio between the movement of thedriving and driven parts may be maintained throughout the range ofmovement of the latter. Only one embodiment of the invention has beenillustrated and described in detail, but it is to be expresslyunderstood that the same is not limited thereto. For example, a fiatreciprocating plate having grooves therein may be employed as thedriving part to produce reciprocating movement of a driven part in adirection at right angles to its own direction of movement. Variousother changes, many of which are suggested in the foregoing description,as well as changes in the design and arrangement of parts illustrated,may also be made without departing from the spirit and scope of theinvention, as will now be apparent to those skilled in the art. For adefinition of .the limits of the invention, reference will be hadprimarily to the appended claims.

What is claimed is:

1. In apparatus of the class described, a rotatably mounted cylindricalmember having an endless thread thereon constituted by two reverselydirected helical grooves, an element movable in a line parallel to theaxis of rotation of said member and having a portion projecting intosaid thread, and guide means on said projecting portion provided with arectilinear portion adapted to engage the walls of said grooves wherebythe reversal of movement of said element at the point of juncture ofthe. grooves is obtained without disturbing the ratio of movementbetween said cylindrical member and said element.

2. In apparatus of the class described, a rotatably mounted cylindricalmember having an endless thread thereon constituted by two reverselydirected helical grooves, an element movable in a line parallel to theaxis of rotation of said member and having a portion projecting intosaid thread, a roller on said projecting portion having a diameterslightly less than the width of said grooves, and a polygonal guidemember on said projecting portion having sides parallel to the walls ofeach of said grooves at the point of juncture of the latter.

3. In apparatus of the class described, a rotatably mounted cylindricalmemberhaving an endless thread thereon constituted by two reverselydirected helical grooves, an element movable in a line parallel to theaxis of rotation of said member and having a portion projecting intosaid thread, and a polygonal guide member on said projecting portionhaving sides parallel to and engageable with the walls of each of saidgrooves adjacent the point of juncture of the latter.

4. In apparatus of the class described, a rotatably mounted cylindricalmember having an endless thread thereon constituted by two reverselydirected helical grooves, an element movable in a line parallel to theaxis of rotation of said member and having a portion projecting intosaid thread, and polygonal guide means on said projecting portion toguide said portion from one of said grooves into the other at thejuncture of said grooves without relative angular movement between saidprojecting portion and guide means.

5. In apparatus of the class described, a rotatably mounted cylindricalmember having an endless thread thereon constituted by two reverselydirected helical grooves, an element movable in a line parallel to theaxis of rotation of said member and having a portion projecting intosaid thread, a roller on said projecting portion having a diameterslightly less than the width of said grooves, a guide having a lengthgreater than the width of said grooves revolvably mounted on saidprojecting portion and entering said thread to only a portion of thedepth thereof, said cylinder having a cut-away portion to permit turningof said guide from one groove into the other adjacent the point ofjuncture of said grooves, and a polygonal guide member on saidprojecting portion having sides parallel to and engageable with theWalls of each of said grooves adjacent the point of juncture of thelatter.

6. In combination, a reversely threaded rotatably mounted cylinder, thereverse threads of which terminate atv an intersection thereof withoutchange of pitch, a member movable linearly in a line parallel to theaxis of said cylinder when the latter is rotated, and an element mountedon said movable member having two pairs of parallel sides engageablewith the walls of said reverse threads.

7. In combination, a member having grooves therein which join at anintersection thereof, means for moving said member, an element extending into said grooves and adapted to be moved relative to saidmember by force exerted by the walls of said grooves, and a guide onsaid element having two sides thereof parallel to the walls of one ofsaid grooves and two sides parallel to the walls of the other of saidgrooves, the perpendicular distance between said parallel sides beingslightly less than the width of said grooves.

8. The combination of a rotatable member, an endless cam groove in theperipheral surface of said member, said groove having a sharp angularturn therein, an element adapted to move in a line parallel to the axisof rotation of said member, and rectilinear guide means on said elementcoacting with said cam groove during rotation of said member, the centerof said guide means thereby being constrained to continuously follow thecenter line of said grooves.

9. In apparatus wherein an element is adapted to be reciprocated bycoaction with a sharp angular groove in a member movable relativethereto, the combination with said element and member of astraight-sided polygonal guide member mounted thereon and extending intosaid groove, said guide member having two sides thereof in substantialengagement with the walls of said groove at all times, whereby the ratiobetween the movements of said element and relatively movable member maybe maintained constant.

10. In a device of the class described, a member having a groove thereonforming a path in one direction, a sharp bend in said groove wherebysaid groove forms a path in a second direction, and an elementprojecting into said groove, comprising means guiding said elementcontinuously in the direction of the first path until said second pathis completely entered by said element.

11. In a device of the class described, a rotatable member, a membermovable in a line parallel to the axis of rotation of said rotatablemember, two reversely directed helical grooves on one of said membersand a portion on the other of said members projecting into said grooves,guide means on said projecting portion adapted to engage the walls ofsaid grooves whereby the reversal of movement of said element at thepoint of juncture of the grooves is obtained without changing the ratioof movement between said cylindrical member and said element.

12. In a device of the character described, a rotatable element, anelement movable in a line parallel to the axis of rotation of saidrotatable element, means on one of said elements constituting tworeversely directed helical walls, and a portion on the other of saidelements abutting said walls, comprising rectilinear guide means wherebysaid other element is projected in the direction of one of said wallsuntil it abuts the other of said walls.

13. In a device of the class described, a member having a groove thereinforming a path in one direction, a sharp bend in said groove wherebysaid groove forms a path in a second direction, an element projectinginto said groove, means on said element providing rolling frictionbetween said element and groove, and means whereby said rolling frictionis changed to sliding friction in proximity to said bend whereby theratio of movement between said grooved member and said element ismaintained constant throughout the movement of said element.

RALPH R. CHAPPELL. RUTGER B. COLT.

